The goals of this project are: 1) to continue the refinement of atomic coordinates of the Fab fragment from human myeloma immunoglobulin IgG New, for which a three-dimensional model has been obtained by single crystal X-ray diffraction analysis; 2) to continue the determination of the amino acid sequence and three-dimensional structure of the Fab fragment from human immunoglobulin IgG Hil, a cryoglobulin; 3) to study the three-dimensional structure of the pFc' fragment from guinea pig immunoglobulins (gamma-1). These studies will be carried out using automatic amino acid sequencing and single crystal X-ray diffraction techniques.